1. Field
This invention relates to a hatch that provides access to a sub-surface facility, such a utility space. More particularly, the hatch includes a watertight seal that is precisely controlled to prevent leakage through the seal due to under-tightening and damage to the seal due to over-tightening.
2. Description of the Related Art
There are numerous hatches having a top surface flush with another surface, such as a sidewalk or roadway. These hatches provide access to an underlying sub-surface facility. The subsurface facilities frequently contain utility lines, such as power lines or communication lines. It is desirable to prevent the ingress of water, such as during a rainstorm or flood. In the manufacture of hatches, it is known to include a compressible material, such as a gasket, in the assembly to provide a watertight seal. The hatch may be sealed with a plurality of fasteners. As these fasteners are tightened, a penetration force is applied to the compressible material. If the penetration force is too low, a watertight seal is not achieved. If the penetration force is too high, the compressible material is permanently deformed causing a failure in the watertight seal.
An accurate penetration force may be achieved by use of a torque wrench or by accurate measurement of the penetration depth. However, it is desirable to minimize the tools carried by a worker and maximize worker efficiency and these options are not ideal.
U.S. Pat. No. 4,441,724 to Taylor discloses a threaded post that extends through a gasket to prevent undue crushing of gasket. U.S. Pat. No. 4,768,684 to Dugge discloses and I-shaped metallic spacer that controls the deformation of two gaskets located along the narrowed central portion of the spacer. The disclosed systems are not intended for repeated opening and closing. They require a skilled person utilizing tools, gages and specialized fixtures to install. Both U.S. Pat. No. 4,441,724 and U.S. Pat. No. 7,768,684 are incorporated by reference herein in their entireties.
In both disclosures above, spacer accuracy must be carefully controlled and the seal is not intended for frequent opening and closing. There remains, therefore, a need for a watertight seal for a hatch that is frequently opened and closed that is not subject to the above disadvantages.